Here's another tool in the activist investor kit: calling a special meeting.

A noted activist investor just this week called for a special meeting at a portfolio company: Clinton Group did so at ValueVision Media, an online shopping service.

Special meetings don't just allow investors to accelerate change, without waiting months for the next annual meeting. They also give investors some interesting strategic leverage over management.

We've put together a guide for investors about special shareholder meetings. This goes with our earlier guides about exempt solicitations and consent solicitations, other tools that investors should know. We discuss special shareholder meetings in a current blog post.